Covalently Grafted 4-Aminopyridine-Reduced Graphene Oxide-Modified Screen-Printed Carbon Electrode for Electrochemical Sensing of Lead Ions

Herein, graphene oxide (GO) was synthesized using a standard and well-known chemical method (Hummer’s). Whereas for the first time, reduced graphene oxide (rGO) was prepared using a simple greener method involving aqueous floral extract of Clitoria ternatea (CT) as a green reducer. The 4-aminopyridine (4AP) organic heterocyclic molecule was covalently grafted on the rGO layer via reaction of nucleophilic substitution. The prepared materials were analysed by Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction measurements (XRD), and scanning electron microscopy (SEM). A number of experimental conditions including scan rate, pH, supporting electrolytes, applied voltage and incubation time were investigated to optimize conditions for obtaining strong signal of the target analyte. The 4AP-rGO/SPCE nanocomposites offer intriguing application prospects in electrochemical lead ion sensors. The 4AP functional on rGO improves the electrochemical performance of the electrode. A 4AP-rGO/SPCE-modified screen-printed carbon electrode exhibits high sensitivity of 0.043 µA pM −1 for lead ion sensing, having a low detection limit (LOD) of 0.597 pM. These results demonstrate the capabilities of the 4AP-rGO/SPCE electrode adopted for the development of highly sensitive electrochemical lead ion sensors by employing differential pulse voltammetry (DPV). Moreover, designed electrochemical sensor was successfully employed to detect lead ions in tap water sample.